You wrote:
>I had problems figuring out the Depth of Field data for EF lenses
>at the Canon Camera Museum:
> http://www.canon.com/camera%2Dmuseum/
>
>But Canon's numbers do not seem to agree with several online DOF
>calculators. E.g. Java DOF at Photozone:
>http://www.photozone.de/depth.htm
>or the Javascript ones: http://members.home.net/gillettm/DOF.html
> http://javascript.internet.com/calculators/field%2Ddepth.html
>Which one(s) are correct?
>On what planet do Canon's number apply?
>What sharpness criteria does Canon use? 3"x5" prints viewed at 5"?
Very funny, Julian! I especially like your title "confusion". Clever!
For those that didn't get it, Julian was playing on one of the components in
the mathematical formula for depth of field; 'Circle of Confusion'. And
there is the difference in the tables. The Canon Museum, though unstated,
calculates to be using a 'Circle of Confusion' of .032mm and Photozone is
using .02mm. This number varies with film format size and intended use.
The lower the 'circle of confusion' the finer the detail in the output. For
example Photozone says:
"0.03mm (circle-diameter) represents the common standard which is usable for
small prints or low-end needs"
"0.025mm - for posters"
"0.02mm - professional level (also for slides)"
"0.01mm - this level is oriented at the resolution of an average film or
lens (about 100 lines/mm=0.01mm). The calculated Depth-of-Field will be
sharp by any standard !"
Art
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